Steroids, such as testosterone and estradiol, have dramatic effects on the brain. Research has traditionally focused on sex steroids produced by the gonads and adrenals. However, recent data indicate that the brain and spinal cord can also produce steroids ("neurosteroids"). Data are accumulating on the locations of steroidogenic enzymes in the brain and on neurosteroid levels in the brain. However, the regulation and functions of neurosteroids remain unclear. The regulation of steroidogenic enzymes in the brain may be critical for their function, as in the gonads and adrenals. This proposal addresses the regulation of neural steroidogenic enzymes in the avian brain. The first study will assess the effects of gonadectomy on the expression of genes for steroidogenic enzymes in brain, using in situ hybridization, Northern blots, and RT-PCR/Southern blots. The second study will investigate the regulation of neural steroidogenic enzymes in vitro. In primary cell cultures, regional differences in enzyme activities will be measured in both sexes. The effects of cAMP and sex steroids on enzyme activities will also be tested. These data will fill critical gaps in the new field of neurosteroids and be relevant for understanding the regulation of neurosteroids in the other vertebrates, including humans.